A system for measuring the location of a vehicle by use of GPS (Global Positioning System) is in popular use (refer to PTL 1, for example).
However, if a system based on GPS cannot receive electromagnetic waves from a GPS satellite, such a system cannot correctly measure the location of the vehicle. This trouble is especially conspicuous in urban areas where buildings are crowded. In addition, the measuring accuracy of GPS in private use is approximately 10 meters that is not accurate enough.
Therefore, in these days, the development of technologies for recognizing vehicle locations by use of SLAM (Simultaneous Localization and Mapping) is under way. Use of SLAM provides an accuracy of as short as several centimeters in the recognition of vehicle locations without considering electromagnetic-wave receiving conditions.